One answer involves an experiment in phytoremediation, the use of plants to help purify the interior environment, undertaken with Rensselaer Polytechnic Institute.
Exhaust air from a training room is pumped out through ductwork to a ceiling diffuser in a nearby corridor. As the air falls from the diffuser, it is gently pulled into a grid of permeable planters lining the corridor and carried through the plants’ root systems. These act as a filter.
The cleaned air is then pumped back to the training room in a relatively closed circuit that will permit architects and engineers to measure the system’s efficacy. Whatever else, it offers a breath of greenery within the mechanical cube.The article links to a RPI press release about this technique; a brief Google search reveals some NASA research into using plants to remove indoor VOCs. I guess the question I have is this - do the plants/dirt actually absorb the compounds (decane, etc) or do they metabolize them? Probably the former, I suspect, which may mean the plants/dirt need to be replaced?